This invention relates to an electronic watch module for electrically connecting a cell to the watch circuit. It is more particularly concerned with a module able to adapt the polarity of the electrodes of the cell to the polarity of the circuit supply terminals.
The cells used in electronic watches are outwardly all similar. They consist of a metal pot-like container of cylindrical shape and of a metal lid which fluidtightly closes off the pot, the lid and the pot being moreover electrically insulated from each other. Depending on the energy capacity of the cell, its size will vary but its general shape remains the same.
Until recently only mercury and silver cells could interchangeably be used in watches with the pot providing the positive electrode, the lid providing the negative electrode.
The cell is housed in a recess provided for that purpose in the watch plate. The recess, which is fitted with a pair of terminals that come into contact with the electrodes, is sized to house a cell having a capacity adapted to the power consumption of the circuit. The terminals, one of which may be clamp-like, are connected to the watch circuit to supply it with voltage of set polarity.
To enable cells of different capacities to be used in one kind of watch or movement, it is known to modify the size of the recess, e.g. by means of removable inserts or spacers.
The cylindrical shape of the cell also enables it to be fitted into the recess in two different ways, either with the lid on top or at the bottom. To enable the circuit to be supplied with the correct polarity regardless of the cell's position in the recess, it is also known to use terminals having a particular shape. The polarity of the cell must of course be well defined.
Lately, lithium cells have been put on the market. They have the advantage over conventional cells of there being very little self-discharge and no likelihood of electrolyte leakage. As regards voltage capacity and size, these new cells are suitable as watch cells but the polarity of their electrodes is the opposite of that of mercury or silver cells, the pot of a lithium cell providing the negative electrode and the lid providing the positive electrode.
Consequently, a conventional mercury or silver cell cannot be replaced by a lithium cell and vice versa in known watches. This is a considerable drawback since it restricts the range of choices among existing cells.